package com.lvxtech.gateway.common.filter;

import java.util.ArrayList;

import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.GlobalFilter;
import org.springframework.cloud.gateway.filter.NettyWriteResponseFilter;
import org.springframework.core.Ordered;
import org.springframework.http.HttpHeaders;
import org.springframework.web.server.ServerWebExchange;

import reactor.core.publisher.Mono;

public class CorsResponseHeaderFilter implements GlobalFilter, Ordered {
	 @Override
	    public int getOrder() {
	        // 指定此过滤器位于NettyWriteResponseFilter之后
	        // 即待处理完响应体后接着处理响应头
	        return NettyWriteResponseFilter.WRITE_RESPONSE_FILTER_ORDER + 1;
	    }

	    @Override
	    @SuppressWarnings("serial")
	    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
	        return chain.filter(exchange).then(Mono.defer(() -> {
	            exchange.getResponse().getHeaders().entrySet().stream()
	                    .filter(kv -> (kv.getValue() != null && kv.getValue().size() > 1))
	                    .filter(kv -> (kv.getKey().equals(HttpHeaders.ACCESS_CONTROL_ALLOW_ORIGIN)
	                            || kv.getKey().equals(HttpHeaders.ACCESS_CONTROL_ALLOW_CREDENTIALS)))
	                    .forEach(kv ->{
	                        kv.setValue(new ArrayList<String>() {{
	                            add(kv.getValue().get(0));
	                        }});
	                    });

	            return chain.filter(exchange);
	        }));
	    }
}
